As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems.
Information handling systems and methods for controlling data transfer to and from a memory storage system are known in the art. For example, FIGS. 1 and 2 illustrate examples of such known prior art systems. FIG. 1 shows a prior art information handling system 100 having a server 101 coupled to a memory storage system 102. The information handling system 100 may include a storage memory controller card within or independent of the server 101. FIG. 2 shows a prior art storage memory controller card with battery back up and a discharge circuit that may be coupled to a redundant array of independent disks (RAID) memory system. A RAID system is a data storage system wherein data is distributed across a group of storage hard disk drives functioning as a small storage unit. Often, information stored on each disk is duplicated on other disks in the array, creating redundancy to ensure no information is lost if disk failure occurs.
An exemplary RAID controller circuit 200, for example a PowerEdge RAID Controller (PERC) card available from Dell, Inc., is shown in FIG. 2. As shown in FIG. 2, the controller circuit 200 includes a cache memory 202 to improve storage performance as described below. The cache memory 202 may be for example DRAM memory such as 256 MB DDR2 memory. During operation of the controller circuit 200, user data may be transferred to/from the controller circuit 200 from/to the RAID hard disk drives (not shown in FIG. 2). As part of the transfer, prior art systems typically store data in the cache memory 202 as part of the transfer of the data to/from the RAID disk drives. If a system power loss occurs it is advantageous to be able to maintain the data transfer of the data that has already been staged in the memory cache. Thus, a backup battery system 204 containing an integrated smart battery controller or Battery Management Unit (BMU) 254 is utilized to provide power to the cache memory 202 so that the memory cache does not lose the data that has not yet been transferred. The battery power may thus power the memory cache until the system power becomes stable again so that data in the cache may then be reliably transferred to the RAID hard disk drives. In one example, the backup battery system 204 provides power to the memory 202 via a DC to DC converter 203, which may provide a 1.8V 1 W power source to the memory 202.
Over time, the health of backup battery 204 can degrade such that the total charge capacity can be significantly less than that of the original battery rating. Such degradation will impact the ability to help ensure the proper transfer of data during a power loss as described above and it is desirable to determine if backup battery 204 has degraded to the point that it does not have sufficient power to accomplish this task. To determine the health of the battery system 204, the controller circuit 200 performs a learn cycle, which includes discharging the battery system 204 completely, then recharging it to its maximum capacity. During the recharge cycle, a management controller measures a charge rate and time to determine the total charge capacity of the battery system 204, and thus its health. Current art methods of discharging a battery system 204 utilize a set of power resistors to drain the charge from the battery system 204 at a rate of 4 W.
Other exemplary portions of the prior art RAID controller card 200 will now be described. The battery system 204 is charged by a charger 206 which is provided power through by a PCI Express X8 Card Edge Connector 205. The battery system 204 sends power to a discharge circuit 211 which include power resistors 215 and a switch 217. When testing for the health of the battery system 204, the discharge circuit 211 receives input from a RAID processor 208 which turns on the switch 217 and thus discharges the battery system 204 through the power resistors 215. The Card Edge Connector 205 provides power to a second DC to DC converter 207. The DC to DC converter 207 provides a plurality of voltage supplies for operating the various components of the circuit during normal non-power loss situations (for example power is shown as being provided to the RAID processor 208). For example, the DC to DC converter 207 may be rated to provide 1.8V 21 W power. Power may be provided from the DC to DC converter 207 to the cache memory 202 through an isolation circuit 210. The isolation circuit 210 is responsive to power good logic 209. When a power loss situation occurs, power good logic 209 sends a signal to the isolation circuit 210 so that the input power supply line to the cache memory will be isolated from other circuitry (this isolates the input power supply line to receive battery power without the battery power being drained to other circuitry on the controller card 200). As shown, controller card 200 also includes battery system data bus (SMBus) 290 for providing battery state information, such as battery voltage, to RAID controller or processor 208.
When a graceful shutdown of RAID controller circuit 200 occurs, backup battery 204 does not power memory 202 of RAID controller circuit 200. However, current drain on battery 204 still occurs due to result of leakage current, which is the driving factor for the shelf life of backup battery 204.
It is common for servers purchased by businesses customers from computer manufacturers to have long deployment times. For example, department or discount stores may place purchase orders for large numbers of servers, and then to store these servers in various local warehouses across the world. When the store has a server failure, a new system is immediately pulled from the nearest local warehouse to replace the failed system. In some cases, the new replacement system that is being deployed may have been sitting in the warehouse in an inactive state for as long as 2 years. This type of long shelf life can be problematic for RAID controller cards, which contain a battery such as battery system 204 of FIG. 2. The integrated smart battery controller of battery system 204 combined with the natural discharge of the battery, can provide a load that depletes the battery charge in as little as six months.
Two methods are commonly employed to limit battery discharge from battery packs in smart battery applications and battery gas gauge designs of portable information handling systems such as notebook computers to maximize battery run-time, which is critical for portable information system operation. These methods may also be used by BMU 254 of battery system 204 of the RAID controller circuit 200 of FIG. 2 to control discharge time from battery cells 258 by discharge field effect transistor (“FET”) 252. These two methods are illustrated in the plot of voltage and relative state of charge (RSOC) versus battery capacity in FIG. 3 for battery backup system 204 under current leakage conditions, and are known as end of discharge voltage (EDV) and RSOC methods. EDV may be found used in almost all gas gauge designs of portable information handling system battery packs (and is also used in RAID controller battery backup packs), and is illustrated by point B in FIG. 3 where battery voltage is discharged from 4.2 volts to a specified end voltage of 3.0 volts in this example, at which point the portable information handling system is shut down at the system level by the operating system running on the main CPU of the system. A RSOC method is a default power management methodology employed by some computer main operating systems such as Microsoft Windows, and is illustrated by point A in FIG. 3 where the battery is discharged to a specific relative charge percentage (e.g., 3% of full charge in this case) before the operating system running on the main CPU of the system takes steps to reduce or terminate power consumption at the system level (e.g., by shutting down the system).